I started drinking Yerba Mate tea, it has something like caffeine that's a bit of a stimulant but not with some of the worse side effects of caffeine. Or it's actually caffeine, there's apparently not a complete consensus :p Anyway whatever it is as long as I only use 1 or 2 teabags a day I don't feel tense and it doesn't keep me up at night. And even after a couple weeks of drinking it I was able to skip a few days without any of that "oh god caffeine withdrawal sluggish throbbing headache want to curl up and die" when I was on the daily coffee pony. So I ordered a couple pounds and we'll see what kicking it up a notch does
I guess it's a big drink in South America.
Downside: The first few times it tastes like boiled old moldy sweatsocks, but it grew on me and now I kinda like the taste.
Fake edit: Argh I shouldn't have looked at
http://en.wikipedia.org/wiki/Yerba_mate - I guess it really is caffeine but in smaller amounts than coffee or black tea, and the xanthines also help reduce some of the effects. And oh boy it's associated with throat and larynx cancer, but probably because of the custom of drinking it pretty hot. And it may reduce cholesterol a bit, have antioxidant properties and stimulate heart regeneration. Oh well I bought it I'm gonna drink it...
Oh one other thing that helped with my endurance during the day is to force myself to eat a decent amount of protein at breakfast and lunch, with some complex carbohydrates. So oatmeal+flaxseed, eggs, or even if I don't feel like eating much I'll eat at least a few handfuls of almonds or other nuts. And I cut down the size of lunch so I lost that groggy feeling afterwards and make up for it by eating the other half of the sandwich later, or snacking on a nut/raisin/seed mix in between meals.
Even with that a lot of days are so go-go-go that I take a power nap at 5 or 6pm, I set a timer for 30-40 minutes in a nice dark quiet room, especially if I have a bunch of stuff to do in the evening. Sometimes I don't even fall asleep but still feel a lot more refreshed afterwards. Even 10 minutes makes a surprisingly big difference. Basically if you go right into heavy REM sleep as soon as you close your eyes you REALLY NEEDED to sleep. I see in hindsight a lot of my problems were from sleep debt, that I tried to counteract with more and more coffee, which made me sleep worse on top of trying to jam too much in at night - vicious circle...